Electrical commutator



R. S. DAHL.

ELECTRICAL COMMUTATOR. APPLICATION FlLED car. 27, I919.

Patented Dec. 14, 1920.

'3 @em Wz J PATENT OFFICE.

RICHARD SMITH DAI-IL, OF CHARLOTTENLUND, NEAR COPENHAGEN, DENMARK.

ELECTRICAL COMMUTATOR.

Application filed October 27, 1919.

To all whom it may concern: I

Be it known that I, RICHARD SrirrH DAHL, subject of the King of Denmark, residing at Charlottenlund, near Copenhagen, Denmark, have invented new and useful Improvements in Electrical commutators, of which the following is a specification.

The invention is an arrangement in electrical commutators by which the commutator segments and the insulating layers between the latter are held together by means of projecting flanges on a core or bush of insulating material, which is shaped under high mechanical pressure, it being in liquid or pulverized state pressed into the cavity formed by the segments when the latter are placed side by side in the shape of a ring, the insulating mass in the said cavity hardening or solidifying so as to became a compact hard core fitting tightly against the segments and forming the hub or sleeve of the commutator, and the distinguishing feature of the invention is that the segments encircle the flanges on the commutator sleeve which serve to fasten them and hold them together, the said flanges fitting into and being formed in suitably shaped, for instance dove-tailed or T-shaped recesses in the segment edges facing the commutator shaft.

By this construction of commutators the advantage is attained that the security against fracture of the commutator sleeve while the commutator is used becomes considerably greater than by the heretofore known commutators of this kind by which the flanges serving to hold the segments in position encircle the segments, in so far as they fit into wedge-shaped notches at the segment ends in the same manner as the clamping rings on commutators of ordinary known kind. The said flanges get thereby a shape which causes the flanges, during the rotation of the commutator to be exposed to very forcible tension and bending, so that they frequently burst by action of the centrifugal force. This is especially the case with commutators of considerable length, it being never possible, by the heretofore used constructions, to use more than two, and for that matter never less than two, flanges to keep each commutator together, and the strain on each of the flanges will therefore increase largely with the length of the commutator. In case of the commutator constructed according to the present invention, on the contrary, there may be used either one Specification of Letters Patent.

Patented Dec. 14, 1920.

Serial No. 333,732.

single segment-fastening flange or several distributed along the entire length of the commutator.

On the drawings, Figures 1 and 2 show longitudinal sections of two different constructions of the invention.

Fig. 3 is a fragmentary transverse section through the middle of Fig. 2.

In the construction sh wn in Fig. 1, each segment 2 and equally each insulating layer 12 has, on the edge facing the shaft 1, only one single and, in'the construction shown, essentially T-shaped recess, wherein the circular flange 3 on the commutator sleeve 4, which serves to hold the segments together is formed by liquid or pulverized insulating material, for instance bakelite, being pressed into the cavity produced within the ring formed by the commutator segments being oined together in known manner.

In the construction shown in Fig. 2, each segment 2 and insulation 12 is fitted with several T-shaped recesses on the edge facing the shaft, so that a corresponding number of circular fastening flanges 3 for the segments are formed. If these, as shown, are distributed evenly along the commutator, any outward bulging of the central portion of the segments due to rotation of the commutator will be effectively prevented.

When centrifugal force is acting, the flanges 3 will be exposed to radially directed tensile and shearing stresses. Of these the tensile stress is the one against which the insulating material offers the lesser resistance, but by the shape and construction of commutators here specified the advantage is attained that the flanges may always be made so wide that the tensile stress may always be 'kept within the permissible limit, even in case of very high rotary speeds.

The portions of the sleeve 4 which are most exposed to fracture are those located nearest to the end faces thereof. These sleeve-portions may be reinforced considerably, as shown in Figs. 1 and 2, by letting the segment ends form, on the side facing the shaft 1, two inwardly directed and toward one another slanting lugs 5 and 6, whereby there will be produced, on the ends of the commutator sleeves, two circular reinforcing flanges 7 located between the said lugs on the end faces of the commutator.

The sleeve 4 may be fastened either, as shown in Fig. 1, directly on the shaft of the motor concerned or, as shown in Fig. 2,

2. A commutator comprising an annular series of commutator bars, insulating layers alternating with and located between the bars, said bars and layers havin end portions extending toward the center, undercut on their sides toward the middle, and a body of molded insulating compound,holding said bars and layers in place, said insulating body being formed with annular flanges near its opposite ends engaging the undercut portions of such bars and layers.

3. A commutator comprising an annular series of commutator bars and insulating layers alternating therewith, said bars and layers extending from end to end or the commutator and having their ends extended toward the center and undercut on their sides toward the middle, and a body of molded insulating compound within the bars and layers, having, near opposite ends, annular flange portions whereby to hold said bars and layers in place.

t. A commutator comprising commutator bars and intervening insulating layers, form-2d at their opposite ends with portions projecting obliquely inwardly and toward each other, combined with a body of molded insulating compound within the bars and layers, having an annular flange portion engaging such projecting portions.

5. A commutator comprising an annular series of commutator bars and intervening insulating layers, extending from end to end of the commutator, said bars and layers having at their ends undercut portions projecting inwardly toward each other, and having etween them undercut portions projecting inwardly, and a body of molded insulating compound filling the space within the bars and layers and engaging the undercut portions thereof.

In witness whereof I have hereunto signed my name in the presence of two subscribing witnesses.

RICHARD SMITH DAHL. Witnesses CARL ll'lEMMINGSEN, C. T., U. BANG. 

